Translational pharmacology of (+)-terrein: from biological activity to oral and periodontal therapeutic development

Previous terrein reviews have emphasized its isolation, synthesis, production, and broad biological activities. Among the prior reviews identified in the literature, no oral/dental indication-specific critical appraisal was found that integrated chemical comparability, evidence directness, exposure, target engagement, formulation, safety, and reproducibility. The present review therefore critically appraised (+)-terrein as a focused case study in oral translational pharmacology and as a model for examining natural-product drug-development bottlenecks. Terrein-specific literature searches were updated through 14 September 2026 in PubMed/MEDLINE, Scopus, and Web of Science Core Collection. The three database searches identified 411 records; after removal of 160 duplicates, 251 unique records remained. Application of predefined eligibility criteria yielded 61 original studies forming the qualitative evidence base, of which 27 underwent structured in-depth appraisal using explicit author-defined criteria. Recurrent biological activity was reported across multiple experimental contexts and by groups without author overlap with the principal oral/skeletal research network, whereas the integrated oral/skeletal evidence sequence remains concentrated within an overlapping collaborative network. Early studies employed fungus-isolated, racemic, or incompletely comparable preparations, whereas later periodontal and skeletal studies predominantly used synthetic (+)-terrein. Biochemical inhibition of the 20S proteasome has been reported at relatively high concentrations; however, no dominant molecular target has been pharmacologically validated at exposure levels corresponding to the key periodontal cellular models. Formal parent-compound pharmacokinetics, periodontal tissue-exposure data, and a clinically relevant oral/periodontal formulation also remain unavailable. A tumor-targeted nanocarrier study provides proof-of-concept for formulation but does not establish oral exposure or periodontal delivery. Among the indications examined, periodontitis provides the most integrated preclinical sequence, linking responses in human gingival fibroblasts, osteoclast inhibition, and a disease-specific mouse model. In that model, the reduction in micro-CT–assessed alveolar bone resorption did not reach statistical significance, despite significant osteoclast- and TNF-α-related effects; moreover, dosing represented systemic preventive/early intervention rather than local treatment of established disease. Further development therefore requires chemical standardization, exposure–response characterization, orthogonal target validation, an oral/periodontal formulation, indication-specific safety assessment, and replication of the periodontal findings by an independent laboratory. Collectively, the available evidence supports (+)-terrein as an experimental pharmacological and drug-development scaffold rather than as a clinically validated therapy.